A replaceable cuvette assembly for use in an optical absorbance measurement system for measuring whole-blood hemoglobin parameters or whole-blood bilirubin parameters. The replaceable cuvette assembly includes a cuvette substrate and a cuvette module fixedly connected to the cuvette substrate wherein the cuvette substrate is a support for securing the cuvette assembly within the optical absorbance measurement system. The cuvette module has a sample inlet port, a sample outlet port, an electronic chip assembly, a sample receiving chamber that fluidly communicates with the sample inlet port and the sample outlet port, a first cuvette window, and a second cuvette window forming a portion of the sample receiving chamber. The first cuvette window and the second cuvette window are aligned with each other defining a cuvette optical path length between the first cuvette window and the second cuvette window and disposed within an optical path of the optical absorbance measurement system.